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4 marksAtomic Structure

CAPE Physics Unit 2 · May/June 2024 · Paper 2 · Question 3(b)(iii)

For Millikan's experiment, the charge Q (in Coulombs) on the test droplet and the voltage V (in Volts) of the supply are related by Q = K/V, where K is a constant. Table 2 shows results from a simulated experiment with charge on different droplets and corresponding balance voltages.

Use the graph in (b)(ii) to determine a value for the constant, K.

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Other parts of this question

  1. 3(a)Identify EACH of the components labelled A-F.[6 marks]
  2. 3(b)(i)Complete Column 3 of Table 2.[2 marks]
  3. 3(b)(ii)On the grid provided in Figure 5 on page 17, plot a graph of charge, Q, versus 1/V. Draw the line of best fit through the points.[4 marks]
  4. 3(c)(i)Write the equation expressing the equilibrium between the electrical force on a charge, Q, in a field of strength, E, and the gravitational force on a droplet…[1 mark]
  5. 3(c)(ii)Write the equation relating the magnitude of the electric field, E, to the impressed voltage, V, and plate separation, d.[1 mark]
  6. 3(c)(iii)Write the equation expressing the mass, m, of the droplets in terms of the radius and density.[1 mark]
  7. 3(d)(i)Show that Q is given by the equation Q = (1/V) [(4/3)πr³ρgd] by substituting the equations in (c)(ii) and (iii) into the equation stated in (c)(i).[2 marks]
  8. 3(d)(ii)Hence, deduce an expression for K.[1 mark]
  9. 3(d)(iii)Determine a value for the magnitude of K.[3 marks]
  10. 3(e)(i)State the direction of the buoyancy force.[1 mark]
  11. 3(e)(ii)Calculate the magnitude of the buoyancy force given that the density of air is 1.3 kg m⁻³.[4 marks]

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